DESCRIPTION: Existing data implicates defective MIP expression in the etiology of the inherited cataracts of the Cat, Lop, and Nct mice. This proposal will refine genetic mapping of the mouse MIP gene, and complete the sequencing of the putative mutant MIP genes in these animals. These mutant MIP minigenes will be used to create transgenic mice as a mechanism for exploring how these specific MIP mutations lead to cataract. Also studied will be chimeric mice, taking advantage of the mosaicism as a tool for probing the function of MIP. MIP and other key membrane proteins will be spatially mapped with confocal laser microscopy. Freeze fracture will be used to explore alterations in membrane architecture. Changes in the lens cytoskeleton will be explored using immunofluorescence and confocal microscopy. Intercellular communication will be explored via dye transfer studies. Water channel activity will be studied in an oocyte swelling assay. Both microscopic and radio tracer studies will be used to measure the lens extracellular space for perturbations in water balance